Method and apparatus for sensing water flow through a dishwasher including a vacuum switch

ABSTRACT

A dishwasher includes a water inlet connectable to a water source. A dishwasher element is operable on water received through the inlet. A flow sensor is in fluid communication with the inlet and is operable to generate a control signal indicative of water flow through the inlet. A control apparatus is connected between the dishwasher element and the flow sensor and is operable to inhibit operation of the dishwasher element in response to the control signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to dishwashers, and moreparticularly, to controlling the operation of a water pump or a waterheater of a dishwasher.

2. Background of the Invention

Water pumps and water heaters are commonly used in dishwashers in orderto increase the pressure and temperature, respectively, of the waterused in the dishwasher. The water pump increases the water pressurebefore the water is sprayed on the dishes, thereby improving thecleaning effectiveness of the water. The water heater raises thetemperature of the water before the water is sprayed on the dishes,which also improves the cleaning effectiveness of the water anddissolved detergent.

Both water pumps and water heaters in dishwashers rely on the presenceof water in order to operate properly. In the absence of water, waterpumps and water heaters can overheat, resulting in damage or destructionto the water pumps and water heaters and/or other components of thedishwasher. Moreover, a “dry” water heater poses a fire hazard. Duringnormal operation of the dishwasher this is not a problem because thedishwasher supplies the water heater and water pump with water on whichto operate. The dishwasher automatically opens at least one valve,thereby allowing water to enter the dishwasher, before the dishwasherapplies power to either the water pump or the water heater. Thus, wateris normally present when the water pump and the water heater areoperated.

A problem does arise, however, if water does not enter the dishwasher asintended when the valve is opened. Water may not be available, forinstance, if there is a leak in the valve, a leak in the pipes leadingto the valve, or a failure of the water supply such as if the main watervalve leading to the dishwasher valve is closed. In this event, thedishwasher may apply power to the water pump and/or the water heater onthe assumption that water is present in the dishwasher. Because no wateris, in fact, present, the water heater and/or the water pump mayoverheat and cause damage to themselves and/or to other parts of thedishwasher.

Accordingly, there is a need for a dishwasher that, among other things,(1) prevents the water pump and water heater from operating if water isnot available; and (2) notifies the user of the unavailability of thewater. The present invention addresses these and other needs.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided an improved dishwasher that senses a flow of water into thedishwasher and inhibits operation of the water pump and the water heaterif the flow of water is not present. The dishwasher also indicates to auser that a flow of water is not present so that any plumbing problemscan be corrected.

The present invention comprises, in one embodiment thereof, a dishwasherincluding a water inlet connectable to a water source. A dishwasherelement is operable on water received through the inlet. A flow sensoris in fluid communication with the inlet and is operable to generate acontrol signal indicative of water flow through the inlet. A controlapparatus is connected between the dishwasher element and the flowsensor and is operable to inhibit operation of the dishwasher element inresponse to the control signal.

The present invention comprises, in another embodiment thereof, a methodof operating a dishwasher, including sensing a flow of water through thedishwasher, and inhibiting an operation of the dishwasher dependent uponthe sensing step.

The present invention comprises, in yet another embodiment thereof, adishwasher including a water inlet connectable to a water source. Adishwasher element is operable on water received through the inlet. Aflow sensor assembly is in fluid communication with the inlet and isoperable to generate a control signal indicative of water flow throughthe inlet. The flow sensor assembly includes a flow element configuredto be pushed in a flow direction by the water flow. A biasing devicebiases the flow element in a second direction substantially opposite tothe flow direction. A sensing device senses movement of the flow elementin the flow direction in opposition to the biasing device. A controlapparatus is connected between the dishwasher element and the flowsensor assembly and is operable to inhibit operation of the dishwasherelement in response to the control signal.

The present invention comprises, in a further embodiment thereof, adishwasher including a water inlet connectable to a water source. Adishwasher element is operable on water received through the inlet. Aflow element is disposed within the inlet for movement in response to aflow of the water through the inlet. A sensing device generates acontrol signal as a result of the movement of the flow element. Acontrol apparatus is connected between the dishwasher element and thesensing device and is operable to inhibit operation of the dishwasherelement in response to the control signal.

The present invention comprises, in another embodiment thereof, a methodof operating a dishwasher, including providing a conduit for carrying afluid to the dishwasher. A temperature-sensing device is placed withinthe conduit. It is determined whether there is a flow of fluid in theconduit by using the temperature-sensing device. Operation of at least aportion of the dishwasher is inhibited dependent upon the determiningstep.

The present invention comprises, in a further embodiment thereof, adishwasher including a conduit for carrying a fluid therein. Atemperature-sensing device is disposed within the conduit. An electricalcontroller is coupled to the temperature-sensing device and determineswhether there is a flow of fluid in the conduit based on at least onetemperature sensed by the temperature-sensing device. The electricalcontroller also inhibits operation of at least a portion of thedishwasher dependent upon the at least one temperature sensed by thetemperature-sensing device.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a schematic view of one embodiment of a dishwasher of thepresent invention;

FIG. 2 is a more detailed schematic view of the dishwasher of FIG. 1;

FIG. 3 is a still more detailed schematic view of the dishwasher of FIG.1;

FIG. 4 is an enlarged schematic view of the venturi and vacuum switch ofFIG. 2 with no water flowing through the venturi, and the vacuum switchbeing in its normal, unactuated position;

FIG. 5 is an enlarged schematic view of the venturi and vacuum switch ofFIG. 3 with water flowing through the venturi, and the vacuum switchbeing in its actuated position;

FIG. 6A and FIG. 6B are a flow chart of one embodiment of a method ofthe present invention utilizing the dishwasher of FIG. 3;

FIG. 7 a is a time chart of the method of FIG. 6 in the case where wateris available in the valve;

FIG. 7 b is a time chart of the method of FIG. 6 in the case where wateris not available in the valve;

FIG. 8 is a schematic view of another embodiment of a dishwasher of thepresent invention;

FIG. 9 is a schematic view of yet another embodiment of a dishwasher ofthe present invention;

FIG. 10 is a schematic view of another embodiment of a dishwasher of thepresent invention;

FIG. 11 is an enlarged schematic view of the sensor assembly of thedishwasher of FIG. 10;

FIG. 12 is an enlarged schematic view of another embodiment of a sensorassembly of the present invention;

FIG. 13 is an enlarged schematic view of the sensor assembly of FIG. 12when water is flowing through the tube;

FIG. 14 is a schematic view of yet another embodiment of a dishwasher ofthe present invention, including the sensor assembly of FIG. 12; and

FIG. 15 is a schematic view of a further embodiment of a dishwasher ofthe present invention.

The exemplifications set out herein illustrate preferred embodiments ofthe invention, and such exemplifications are not to be construed aslimiting the scope of the invention in any manner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and more particularly to FIG. 1, anexemplary cleaning appliance 20 constructed according to principles ofthe present invention is shown. For purposes of example and explanation,the cleaning appliance 20 of FIG. 1 is shown as a dishwasher. However,the principles of the present invention may also be applied to othertypes of washing appliances, such as a clothes washer. In FIG. 1, theexemplary dishwasher 20 includes a water basin 22, also known as a sumpor reservoir, a water heater 24 disposed within the basin 22, a waterpump 26, a conduit in the form of an inlet tube 28, a control apparatus29 and an electrically actuated valve 34.

The control apparatus 29, powered by a voltage source 56, controls theoverall operation of the dishwasher 20, including opening the valve 34and optionally applying power to the heater 24 and the pump 26. Moreparticularly, when a user initiates a dishwashing cycle, such as bypushing a button or turning a knob or dial, the control apparatus 29opens the valve 34 to allow water from a water source 85 to pass throughthe inlet tube 28 and flow into the basin 22. The controller 29optionally applies voltage to the heater 24 in order to heat the waterin the basin 22. The controller 29 also applies voltage to the pump 26in order to pump the water out of the basin 22 so that the water can besprayed onto the dishes in the dishwashing chamber (not shown). Thecontroller can also administer other functions of the dishwasher andtiming of the dishwasher operations in a known manner.

As discussed above, damage can be caused by applying power to the heater24 and/or pump 26 in the absence of water. In order to prevent suchdamage, the control apparatus 29 in accordance with the presentinvention verifies that water is flowing through the inlet tube 28before the control apparatus 29 applies power to either the heater 24 orthe pump 26. Specifically, the control apparatus opens the valve 34 toallow water into the inlet tube 28. If the controller 29 senses thatwater is not flowing through the tube 28 after the valve 34 is opened,then the controller 29 prevents the application of power to the heater24 and the pump 26.

In one feature of the invention, the control apparatus 29 includes asensor assembly 31 a cycle controller in the form of timer module 42 anda fault indicator 35, as shown in FIG. 2. The timer module 42 controlsthe timing of the application of voltage to the valve 34, the heater 24and the pump 26. The sensor assembly 31 senses whether water is flowingthrough the tube 28 after the timer module 42 has attempted to open thevalve 34. If the sensor assembly 31 does sense a flow of water, then thetimer module 42 proceeds with normal operation and applies voltage tothe heater 24 and the pump 26. If the sensor assembly 31 does not sensea flow of water, then the sensor assembly 31 prevents the timer module42 from applying voltage to the heater 24 and the pump 26. The sensorassembly 31 also activates the fault indicator 35 to indicate to theuser that no water is flowing through the tube 28 and repairs may beneeded. In certain embodiments of the invention, the controller canterminate all operations of the dishwasher, or can allow the dishwasherto continue through portions or all of its cycle of operation.

Several embodiments of the dishwasher of the present invention,including multiple embodiments of the sensor assembly 31, the timermodule 42 and the fault indicator 35 will be described herein. It is tobe understood that it may be possible in any particular embodiment ofthe dishwasher to swap the sensor assembly 31, the timer module 42and/or the fault indicator 35 with another disclosed embodiment of thesensor assembly 31, the timer module 42 and/or the fault indicator 35within the spirit and scope of the present invention.

In one embodiment shown in FIG. 3, the sensor assembly 31 can include avacuum switch 30, a venturi 32 and a relay 40. The fault indicator 35can include a relay 36 and an indicator lamp 38. The timer module 42 canbe of known construction, and can include a manually operable usercontrol knob 44, a timer motor 46, a plurality of cams 48, 50, 52, 54,and respective associated cam-actuated switches 49, 51, 53, 55. Thecontrol knob 44 and cams 48, 50, 52, 54 are mounted to a cam shaft 57driven by the timer motor 46. Each of the cam-actuated switches 49, 51,53, 55 is mounted adjacent its associated cam in a manner well known inthe appliance control art for sequential actuation of the variousswitches. The cam-actuated switch 49 connects the voltage source 56 tothe valve 34; the cam-actuated switch 51 connects the voltage source 56to the timer motor 46; the cam-actuated switch 53 connects the voltagesource 56 to the water heater 24; and the cam-actuated switch 55connects the voltage source 56 to the water pump 26.

FIG. 4 shows the vacuum switch 30 in greater detail, although stillschematically, in the condition in which no water is flowing past orthrough the venturi 32. The vacuum switch 30 includes a differentialpressure housing 58. A diaphragm 61 is disposed within the housing 58and separates the same into a first chamber 62 and a second chamber 63.The second chamber 63 and the venturi collectively define asubstantially enclosed space.

The housing 58 includes a first port 64 and a second port 65. The firstport 64 is a vent port and fluidly connects the first chamber 62 withthe ambient air. The second port 65 is a venturi opening and fluidlyconnects the second chamber 63 with the venturi 32. The vent port 64 isopen to atmosphere and the venturi's capillary port 65 is in the fluid(water) stream. The diaphragm 61 is sealingly engaged within the vacuumswitch 30 and serves to isolate and separate the chambers 62, 63.

When water flows through the venturi 32, there is a differentialpressure between the first and second chambers 62, 63, respectively.Specifically, the venturi 32 creates a low pressure vacuum at the secondport 65 and in the second chamber 63. Since the pressure at the firstport 64, i.e., atmospheric pressure, is higher than the pressure at thesecond port 65 when the water flows through the venturi 32, the pressurewithin the first chamber 62 is greater than the pressure in the secondchamber 63.

Differential pressure between the first chamber 62 and the secondchamber 63 moves at least a portion of the diaphragm 61. Movement of thediaphragm 61 in turn is used to “trip” the vacuum switch 30, asdiscussed in more detail below.

The diaphragm 61 includes a centrally disposed, planar first section 66.Surrounding or disposed about the first section 66 is a flexible secondsection 67 extending between the first section 66 to where the diaphragm61 engages an interior surface of the housing 58. A connecting member 68includes a first end 69 which engages a first side 70 of the diaphragm61 such that the connecting member 68 is perpendicular to the firstsection 66 of the diaphragm 61. A second end 72 of the connecting member68 is connected to an electrically conductive, flexible switch arm 74.One end of the flexible switch arm 74 is fixedly attached to the housing58 at 75. As the diaphragm 61 deflects due to a pressure differentialbetween the first chamber 62 and the second chamber 63, the switch arm74 bends or flexes such that a distal end of the switch arm 74 movesfrom the contact 78 to the contact 80.

A biasing member 77 in the form of a helical coil spring is disposed inthe second chamber 63. One end of the spring 77 engages an interiorsurface of the housing 58. The other end of the spring 77 interfaceswith the second or low pressure side 79 of the diaphragm 61. The spring77 opposes movement of the diaphragm 61 in the direction of the arrow A.

The switch arm 74 is flexible such that the distal end of the switch arm74 is movable between a fixed, normally closed contact 78 and a fixed,normally open contact 80. In the absence of water flowing through theventuri 32, the spring 77 holds the switch arm 74 in the position shownin FIG. 4 such that the switch arm 74 electrically interconnects thenormally closed contact 78 and the voltage source 56 through a contact76.

The venturi 32 includes a conduit extending between an inlet end 82 andan outlet end 84. The outlet end 84 tapers in a direction of water flow86 (FIG. 5). That is, a width 88 and a cross-sectional area of theoutlet end 84 decreases in the direction of water flow 86.

The operation of the dishwasher 20 will now be described with referenceto the flow chart of FIG. 6. To initiate operation of the dishwasher 20,a user turns the control knob 44. The rotation of the control knob 44causes the cam 50 to rotate and the switch 51 to close, which therebyconnects the voltage source 56 to the timer motor 46 (step 400).

When the voltage is applied to the timer motor 46, the timer motor 46starts to run, turning the cam shaft 57 and the cam 48 until the switch49 closes, thereby connecting the voltage source 56 to the valve 34.When the switch 49 closes, the timer module 42 has entered the fillinterval (step 402) in which the water basin 22 is to be filled withwater.

As voltage is applied to the water valve 34, the valve 34 opens (step404), allowing water from a water source 85, such as a well, municipalwater supply, or water heater, to flow through the valve 34 and theinlet tube 28 in the direction indicated by arrow 86 (FIG. 5). The waterthen flows through the venturi 32 and into the water basin 22. As thewater flows through the outlet end 84 of the venturi 32, the waterincreases speed and causes the pressure at the port 65 to be lower thanthe pressure at the port 64, as is well known in the fluid control art.

FIG. 5 shows the vacuum switch 30 in the condition in which water isflowing through the venturi 32, as indicated by arrows 86. The flow ofthe water creates a vacuum within the second chamber 63 that sucks thediaphragm 61 in the direction of arrow A, overcoming the retaining forceof the spring 77, as shown in FIG. 5. As the diaphragm 61 moves indirection A, the attached connecting member 68 pulls the switch arm 74while following the movement of the diaphragm 61. As the switch arm 74flexes in direction A, the switch arm 74 breaks electrical connectionwith the normally closed contact 78 and comes into electrical contactwith the normally open contact 80 at the end of the movement of theswitch arm 74.

Via the sequence of events described above, the position of the vacuumswitch 30 indicates whether water is flowing through the venturi 32(step 406). More particularly, if the switch arm 74 is electricallyconnected to the normally closed contact 78, it indicates that no wateris flowing through the venturi 32. In this case, power is removed fromthe timer motor 46, as described in more detail below. On the otherhand, if the switch arm 74 is not electrically connected to the normallyclosed contact 78, but rather is electrically connected to the normallyopen contact 80, it indicates that water is flowing through the venturi32. If the switch arm 74 is electrically connected to neither thenormally closed contact 78 nor the normally open contact 80, it mayindicate that there is some partial flow of water in the venturi 32, butnot enough to fully actuate the vacuum switch 30 such that the switcharm 74 contacts the normally open contact 80. If this occurs, thedishwasher will operate in this embodiment as though the vacuum switch30 were fully actuated. However, it is also possible to design thedishwasher so that a partial flow of water is treated the same as atotal absence of water.

As described above, if water is available at the valve 34 when the valveis opened, and if the water is able to flow through the valve 34 andinto the venturi 32, then the switch arm 74 becomes electricallyconnected to the normally open contact 80. Thereby, the voltage source56 is electrically connected to the timer motor 46 through the switcharm 74 and the normally open contact 80 (step 408). This application ofpower to the timer motor 46 via a control signal generated by the vacuumswitch 30 through the normally open contact 80 is redundant in the sensethat power is also simultaneously applied to the timer motor 46 via thecam 50 and switch 51. The redundancy is short-lived, as the powerthrough the switch 51 will soon disappear, as described below. However,the temporary overlap in power supply is necessary in order to ensurethat a possible late actuation of the vacuum switch 30 does not causethe timer motor 46 to lose power completely.

The time chart of FIG. 7 a indicates that the opening of the water valve34 and the application of power to the timer motor 46 through thenormally open contact 80 occur substantially simultaneously. However, itis to be understood that there is some small period of time required forthe water to flow through the opened valve 34, flow through the inlettube 28 and the venturi 32, and actuate the vacuum switch 30. Thus,there is, in actuality, some small period of time between the opening ofthe water valve 34 and the application of power to the timer motor 46through the normally open contact 80. Because this small time period isnegligible in comparison with the other time periods illustrated in FIG.7 a, and for ease of illustration, FIG. 7 a has been simplified in thisrespect.

Before the water flows through the venturi 32, a coil 90 of the relay 40is electrically connected to the voltage source 56 through the switcharm 74 and the normally closed contact 78. The relay 40 can be the typeof relay wherein a magnetic field produced by the coil 90 causes thecontacts 92, 94 of the relay 40 to open from a closed position andremain open so long as the magnetic field is present, as is well knownin the art. As the water flows through the venturi 32, and the switcharm 74 moves out of electrical contact with the normally closed contact78, current through the coil 90 ceases. In the absence of the electricalfield produced by the current through the coil 90, the contacts 92, 94close, thereby providing another current path between the voltage source56 and the timer motor 46 while the water flows through the venturi 32.

As the timer motor 46 continues to run and rotate the cam shaft 57, thefurther rotation of the cam 50 causes the switch 51 to open, therebybreaking the electrical connection between the voltage source 56 and thetimer motor 46 through the switch 51, and ceasing the application ofpower to the timer motor 46 via the cam 50 (step 410). Because theopening of the switch 51 occurs some time after the vacuum switch 30 isactuated, thereby providing power to the timer motor 46 through thenormally open contact 80 and through the contacts 92, 94, power to thetimer motor 46 is not interrupted. That is, as shown in FIG. 7 a, thereis some overlap in time between the application of power to the timermotor 46 via the cam 50 and the application of power to the timer motor46 via the normally open contact 80. However, as described in moredetail below, if there is no water flow through the venturi 32, thenpower will be supplied to the timer motor 46 through neither thenormally open contact 80 nor the contacts 92, 94. In this, case,removing power through the cam 50 and switch 51 will have the effect ofcompletely removing power from the timer motor 46, and therebypreventing the timer motor 46 from applying power to the heater 24 andthe pump 26 in the absence of water.

The current path through the contacts 92, 94 is a lower resistance pathbetween the voltage source 56 and the timer motor 46 than is the currentpath through the switch arm 74 and the normally open contact 80. Thus,the majority of the current from the voltage source 56 to the timermotor 46 is routed through the contacts 92, 94 while water flows pastthe venturi 32.

The timer motor 46 continues to run and rotate the cam shaft 57 as waterflows through the venturi 32. The vacuum switch 30 monitors the waterflow through the venturi 32 and confirms that the water flow continues(step 412) as long as the valve 34 is open. So long as the water flowcontinues, the dishwashing cycle continues and no action is necessary.The vacuum switch 30 continues to monitor the water flow through theventuri 32. If, on the other hand, the vacuum switch 30 determines thatthe water flow through the venturi 32 has ceased, then power is removedfrom the timer motor 46, as discussed in more detail below.

Shortly before the end of the fill interval (step 414), the rotation ofthe cam 50 causes the switch 51 to close, thereby reestablishing boththe electrical connection between the voltage source 56 and the timermotor 46 through the switch 51 and the application of power to the timermotor 46 via the cam 50 (step 416). Thus, power is again appliedredundantly to the timer motor 46 in the sense that power issimultaneously applied via the normally open contact 80.

As the uninterrupted operation of the timer motor 46 continues, therotation of the cam 48 causes the opening of the switch 49 (step 418),which, in turn, removes the application of power to the valve 34. Asvoltage is removed from the water valve 34, the valve 34 closes (step420), stopping the water flow through the valve 34 and the inlet tube28. As the water stops flowing through the venturi 32, the low pressurewithin the second chamber 63 ceases, allowing the spring 77 to push thediaphragm 61 back to the position shown in FIG. 4. The diaphragm 61moves in a direction opposite to the direction of arrow A, therebycausing the switch arm 74 to break electrical connection with thenormally open contact 80 and come into electrical contact with thenormally closed contact 78 at the end of the motion.

The time chart of FIG. 7 a indicates that the closing of the water valve34 and the removal of power to the timer motor 46 through the normallyopen contact 80 occur substantially simultaneously. However, it is to beunderstood that there is some small period of time required for thewater to stop flowing through the valve 34, the inlet tube 28 and pastthe venturi 32, and for the switch arm 74 to break contact with thenormally open contact 80. Thus, there is, in actuality, some smallperiod of time between the closing of the water valve 34 and the removalof power to the timer motor 46 through the normally open contact 80.Because this small time period is negligible in comparison with theother time periods illustrated in FIG. 7 a, and for ease ofillustration, FIG. 7 a has been simplified in this respect.

As the vacuum switch 30 returns to the position of FIG. 4, the switcharm 74 again electrically connects the voltage source 56 to the relay 40via the normally closed contact 78. The coil 90 of the relay 40 isenergized by the control signal voltage generated by the vacuum switch30 and applied across the coil 90. The excitation of the coil 90produces a magnetic field which caused the contacts 92, 94 to open.Thus, with power no longer being supplied to the timer motor 46 via thenormally open contact 80, power to the timer motor 46 is also removedvia the normally closed contact 78 (step 422). Although power to thetimer motor 46 via the contacts 78, 80 is thereby removed, power isstill applied to the timer motor 46 via the switch 51.

Some time after the end of the fill interval, i.e., after water hasstopped flowing past the venturi 32, the operation of the timer motor 46causes power to be applied to the heater 24 and to the pump 26 (step424). More particularly, the operation of the timer motor 46 and therotation of the cam 52 causes the switch 53 to close, therebyelectrically connecting the voltage source 56 and the heater 24. Thepower applied to the heater 24 results in the heating of the water inthe basin 22. Also, the operation of the timer motor 46 and the rotationof the cam 54 causes the switch 55 to close, thereby electricallyconnecting the voltage source 56 and the water pump 26. The water pump26 sprays the heated water from the basin 22 onto the dishes in thewashing chamber (not shown).

Power is applied to the heater 24 and to the pump 26 for somerespective, predetermined time periods before the operation of the timermotor 46 causes power to be removed from the heater 24 and from the pump26 (step 426). More particularly, the rotation of the cam 52 causes theswitch 53 to open and disconnect the voltage source 56 from the heater24. In the embodiment shown in FIG. 7 a, the pump 26 continues to runafter power to the heater 24 has been discontinued, thereby spraying thedishes with water that has been heated previously by the heater 24.However, the further rotation of the cam 54 causes the opening of theswitch 55, which, in turn, removes the application of power to the waterpump 26. The water pump 26 stops spraying water as voltage is removed bythe switch 55. This completes the washing cycle.

If one or more additional washing cycles are required, then the washingphase is not complete (step 428) and the timer motor 46 enters a fillinterval again (step 402). Specifically the cam 48 again causes theswitch 49 to close, thereby beginning another washing cycle. On theother hand, if an additional washing cycle is not required, then thewashing phase is complete (step 428) and the machine may enter a dryingphase (step 430) during which the dishes are dried. After the dryingphase, the continued operation of the timer motor 46 and rotation of thecam 50 causes the switch 51 to open, thereby removing the power to thetimer motor 46 (step 432). At this point, the dishes are ready to beunloaded (step 434).

In the embodiment depicted in FIG. 7 a, the closing of the water valve34 and the removal of power to the timer motor 46 through the normallyopen contact 80 occur substantially simultaneously with the applicationof power to the heater 24 and to the pump 26. However, it is to beunderstood that it is also possible for the first application of powerto the heater and pump to occur at either some point in time before orsome point in time after the end of the water fill interval.

If water is not available at the outlet of the valve 34 when the valve34 is first opened (step 404), perhaps because of a leak in the plumbingleading to the valve 34 or a defect in the valve 34 itself, water doesnot flow through the venturi 32 and the vacuum switch 30 is notactuated. That is, the vacuum switch 30 remains in the position of FIG.4. Thus, the position of the vacuum switch 30 indicates that water isnot flowing through the venturi 32 (step 406).

As the vacuum switch 30 remains in the position of FIG. 4, the switcharm 74 electrically connects the voltage source 56 to the relay 40 viathe normally closed contact 78. A coil 90 of the relay 40 is energizedby the control signal voltage generated by the vacuum switch 30 andapplied across the coil 90. By the contacts 92, 94 remaining open, thevoltage source 56 is completely disconnected from the timer motor 46.Thus, the power to the timer motor 46 is removed via the normally closedcontact 78 (step 436).

As the vacuum switch 30 remains in the position of FIG. 4, the switcharm 74 also electrically connects the voltage source 56 to the relay 36via the normally closed contact 78. A coil 96 of the relay 36 isenergized by the voltage applied across the coil 96. The relay 36 can bea different type of relay than relay 40. That is, the relay 36 can be ofthe type wherein a magnetic field produced by the coil 96 causes thecontacts 98, 100 of the relay to close from an open position and remainclosed so long as the magnetic field is present, as is also well knownin the art. When the contacts 98, 100 are closed, the voltage applied tothe valve 34 by the timer module 42 is also applied to the faultindicator lamp 38. Thus, power is applied to the fault indicator light38 (step 438) when voltage is applied to both the valve 34 and to thenormally closed contact 78. That is, power is applied to the faultindicator light 38 when the valve 34 is opened to make possible a flowof water into the venturi 32, but water does not actually flow throughthe venturi 32, as sensed by the vacuum switch 30.

A delay circuit 102 may be included between the normally closed contact78 and the relay 36 in order to provide a small time delay in thetransmission of the voltage signal from the normally closed contact 78to the relay 36. The time delay prevents the fault indicator light 38from flashing on during the brief reaction time period of the vacuumswitch 30 between the valve 34 being opened and power being removed fromthe normally closed contact 78.

Alternatively, it is possible to not include the delay circuit 102 andallow the fault indicator light 38 to flash on between the applicationof power to the valve 34 and the removal of power to the normally closedcontact 78. The flashing of the light 38 may serve as a indicator to theuser that the light 38 is operational.

The sustained illumination of the fault light 38 indicates to a userthat the water supply to the dishwasher has been interrupted, which maymean a leak needs to be repaired in the inlet tube 28, the valve 34 orthe venturi 32. As in the case where water does flow through the venturi32, the power to the timer motor 46 via the cam 50 is removed (step440).

If the vacuum switch 30 senses that an existing flow of water hasstopped (step 412), then power is removed from the timer motor 46 (step442). More particularly, when the water flow through the venturi 32stops, the switch arm 74 moves into electrical contact with the normallyclosed contact 78, just as in the case when the valve 34 is closed (step420), as discussed above. The subsequent opening of the contacts 92, 94of the relay 40 removes all voltage from the timer motor 46, as theswitch 51 is open at this point in time. When the switch arm 74 iselectrically connected to the normally closed contact 78, the contacts96, 100 of the relay 36 close as a result of the excitation of the coil96, and the fault indicator lamp 38 becomes lit (step 444).

As described above, the dishwasher 20 does not allow power to be appliedto the dishwasher elements, i.e., the heater 24 and the pump 26, whenwater is not flowing through the venturi 32. Specifically, in theabsence of water flow through the venturi 32 when valve 34 is open, thecontacts 92, 94 open to thereby remove power from the timer motor 46,the heater 24 and the pump 26. Thus, the dishwasher 20 prevents thedishwasher elements from operating without the cooling effect of waterand thereby overheating.

In another embodiment of the invention, a dishwasher 120, shown in FIG.8, includes a timer module 142 having a relay 140 with a coil 190 andcontacts 192 and 194. The contacts 192, 194 selectively connect theswitches 53, 55 to the voltage source 56. The switches 53, 55, as in theprevious embodiment, selectively apply the voltage from the voltagesource 56 to the water heater 24 and the water pump 26, respectively.The coil 190 is electrically connected to the output 193 of an AND gate195. The two inputs 197, 199 to the AND gate 195 are connected to theinput of the valve 34 and the normally closed contact 78, respectively.The relay 140 can be of the same type as the relay 40. That is, therelay 140 can be the type of relay wherein a magnetic field produced bythe coil 190 causes the contacts 192, 194 of the relay 140 to open andremain open so long as the magnetic field is present. Other componentsof the dishwasher 120 are the same as shown in FIG. 3.

In operation, the contacts 192, 194 of the relay 140 normally remainclosed, thereby applying power to the switches 53, 55. The cams 52, 54operate to open and close the switches 53, 55, respectively, to therebyselectively apply power to the water heater 24 and the water pump 26,respectively.

When power is applied to open the valve 34, it is possible for amalfunction to occur such that no water passes through the venturi 32,as already described. More particularly, when the timer 142 appliesvoltage to the valve 34 the timer 142 also applies voltage to the input197 of the AND gate 195, i.e., the input 197 of the AND gate 195 is“high”.

If no water flows through the venturi 32, then voltage from the voltagesource 56 is applied to the normally closed contact 78 through theswitch arm 74, as described in more detail with regard to the previousembodiment. The normally closed contact 78 is electrically connected tothe input 199 of the AND gate 195. Thus, if no water flows through theventuri 32, then voltage is applied to the input 199 of the AND gate195, i.e., the input 199 of the AND gate 195 is “high”.

If voltage is applied to the valve 34 (the input 197 is high) and yet nowater flows through the venturi 32 (the input 199 is high), then theoutput 193 of the AND gate 195 is high, and voltage is applied acrossthe coil 190. The magnetic field resulting from current flow through thecoil 190 causes the contacts 192,194 to remain open so long as voltageis applied to the valve 34 and no water flows through the venturi 32.Thus, the dishwasher 120 prevents the heater 24 and the pump 26 fromoperating without the cooling effect of water and thereby overheating.

The AND gate 195 is schematically depicted herein for ease ofexplanation and illustration. However, it is to be understood that theAND gate 195 can be embodied by discrete circuitry, as is known by oneskilled in the art. For instance, the AND gate may be formed of suchdiscrete circuitry in order to source an adequate amount of current todrive the relay 140. Other details of the dishwasher 120 aresubstantially similar to the dishwasher 20, and thus are not discussedin detail herein.

In yet another embodiment (FIG. 9), a dishwasher 220 includes anelectrical controller 242, which may be in the form of a microprocessor.An output 297 of the controller 242 drives the valve 34. The normallyclosed contact 78 is electrically connected to an input 299 of thecontroller 242.

In operation, the controller 242 is powered by voltage received on input256 from the voltage source 56. The controller 242 applies a voltage tothe output 297 and, consequently, to the valve 34 at a predeterminedtime after the dishwasher 220 has been started by a user. Then, if waterflows through the venturi 32, the controller 242 applies voltage to theheater 24 and the pump 26 with timing substantially similar to thetiming depicted in FIG. 7 a. However, if no water, or an insufficientamount of water, flows through the venturi 32, then a voltage is appliedto the input 299 of the controller 242 via the switch arm 74 and thenormally closed contact 78.

If the controller 242 receives a voltage on the input 299 while avoltage is being applied to the output 297, then the controller 242applies no voltage to the outputs 253, 255 to the heater 24 and the pump26, respectively. That is, the controller 242 prevents voltage frombeing applied to either the heater 24 or the pump 26 if, while power isapplied to the valve 34, no water flows though the venturi 32. Thepresence of voltage on input 299 indicates to the controller 242 thatthe switch arm 74 is in contact with the normally closed contact 78, andtherefore no water is flowing through the venturi 32. Conversely, thepresence of voltage on input 280 through the switch arm 74 and thenormally open contact 80 indicates to the controller 242 that water isflowing through the venturi 32 and that power can be applied to theheater 24 and the pump 26.

In general, the controller 242 does not allow any voltage to be appliedto either the heater 24 or the pump 26 so long as no water flows throughthe venturi 32, as indicated by a voltage on the input 299. Thus, thecontroller 242 prevents the heater 24 and the pump 26 from operatingwithout the cooling effect of water and thereby overheating. Otherdetails of the dishwasher 220 are substantially similar to thedishwasher 20, and thus are not discussed in detail herein. Preferably,the controller 242 is microcomputer-based or microprocessor-based.

In another embodiment (not shown), there is a switch between the voltagesource 56 and the switch arm 74. If, after a voltage has been applied toopen the valve 34, there is a signal at the input 299 indicating no flowin the venturi 32, then the controller 242 opens the switch to therebycut all power from the voltage source 56 to the switch arm 74.

In a further embodiment (FIG. 10), a dishwasher 320 includes a valve 34,a water source 85, an inlet tube 328, an electrical controller 342, aflow sensor assembly 330, an indicator lamp 338, a pump 26, a basin 22and a heater 24. The electrical controller 342 is microcomputer-based.

The flow sensor assembly 330 in this embodiment includes a flow elementin the form of a permanent magnet 331, a biasing device in the form of aspring 333, and a sensing device in the form of a coil 335. Both themagnet 331 and the spring 333 are disposed within the tube 328. As shownin FIG. 11, the magnet 331 can be in the form of a hollow sleeve forallowing the water to flow therethrough in direction 86. The coil 335 isdisposed outside of the tube 328 and forms a plurality of wire turnsaround the tube 328 in the area of the magnet 331. Further, the coil 335can substantially surround the magnet 331 such that the magnet 331 isdisposed within the turns of the coil 335. In an alternative embodiment,the coil can be offset to one end of the sleeve so that the sleeve canmove to a position in which it is clear of the coil.

The spring 333 has a downstream end 337 attached to the inside wall ofthe tube 328. An upstream end 339 of the spring 333 can be attached toor bear against a downstream end 341 of the magnet 331. The magnet 331is not directly attached to the tube 328 so that the magnet 331 is freeto translate within the tube 328 in response to water flow. The magnet331 has a surface area facing the incoming water flow that is calibratedto achieve a predetermined pushing force on the magnet 331 at anexpected input flow rate. The two opposite ends 343 and 345 of the coil335 can be electrically connected to the controller 342 or to a currentsensor or circuit.

During operation, the controller 342 applies a voltage to the valve 34on output 397 to thereby open the valve 34 and allow water from thewater source 85 to enter the tube 328. As the water flows in direction86, the magnet 331 is pushed in direction 86 against the bias of thespring 333, thereby compressing the spring 333. As the magnet 331 movesin direction 86, the magnet 331 disturbs the electrical current to becarried in the coil 335, as is well known to those skilled in the art.Thus, the magnet 331 and the coil 335 can operate as an inductivetransducer or sensor. The current in the coil 335 functions as a controlsignal. The electrical controller 342 (or current sensor circuit)evaluates the current in the coil 335 to ultimately determine theposition of the magnet 331 relative to the coil 335.

When the water flow through the tube 328 stops, the spring 333 pushesthe magnet 331 in direction 387, opposite to direction 86. The movementof the magnet 331 again disturbs the electrical current in the coil 335.The electrical controller 342 again evaluates the current in the coil335.

The controller 342 can determine the time duration or time period of thewater flow based upon the status of the current in the coil 335. Moreparticularly, the controller 342 can determine the time duration or timeperiod between the time at which the current in the coil 335 was firstdisturbed as a result of the magnet 331 moving in direction 86 and thetime at which the current in the coil 335 was again disturbed as aresult of the magnet 331 moving in direction 387. This time periodcorresponds to the time period between the point in time at which themagnet 331 started moving in direction 86 as a result of the water flowand the point in time at which the magnet started moving in direction387 as a result of the cessation of the water flow. That is, the timeperiod determined by the controller 342 corresponds to the time periodin which the water flows through the tube 328.

If there are one or more momentary interruptions of the water flow, thenthe controller 342 can determine or measure two or more time periods ofwater flow and add the time periods together in order to determine atotal amount of time in which water flows through the tube 328. Thecontroller 342 can control the operation of the heater 24 and/or thepump 26 based upon the time period or duration of the water flow.Further, it is also possible, with some modifications, for thecontroller 342 to determine a total amount or volume of water that hasflowed through the tube 328 based upon the time period or duration ofthe water flow and knowledge of the water flow rate.

If the controller 342 does not sense a disturbance in the current in thecoil 335 after the valve 34 has been opened, then the controller 342inhibits operation of the dishwasher 320. More particularly, if thecontroller 342 does not sense a disturbance in the current in coil 335after the valve 34 has been opened, then the controller 342 does notsupply a voltage to either the water heater 24 or the water pump 26.That is, no voltage is provided on outputs 353, 355. Rather, thecontroller 342 provides a voltage on output 357 in order to power on afault indicator lamp 338. The lamp 338 indicates to the user that thereis no water flowing through the tube 328 even though power has beenapplied to the valve 34, and hence, there may be a leak that requiresrepair.

As discussed above, it is possible for the controller 342 to prevent theapplication of voltage to the heater 24 and/or the pump 26 if themeasured time duration of the water flow through the tube 328 is below apredetermined threshold. That is, power can be withheld from the heater24 and/or the pump 26 if the time period between the magnet 331 movingin direction 86 and then moving back in direction 387 is inadequate toprovide a large enough volume of water for the required cooling effectfor the dishwasher elements 24, 26. The controller 342 can alsoterminate a dishwasher cycle if the measured time duration of the waterflow through the tube 328 is below the predetermined threshold. Further,the controller 342 can power on the fault indicator light 338 toindicate to a user that the amount of water that has flowed through theinlet tube 328, as calculated or estimated based upon the measured timeduration of the water flow through the tube 328, is insufficient forproper dishwasher operation.

Similarly, it is also possible for the controller 242 of FIG. 9 toprevent the application of voltage to the heater 24 and/or the pump 26if the measured time duration of the water flow through the tube 28 isbelow a predetermined threshold. Such a measured time duration wouldcorrespond to the time period in which a voltage is present at the input280 of the controller 242. Further, any embodiment disclosed herein thatincludes the use of a microcomputer-based controller is capable ofpreventing the application of voltage to the heater 24 and/or the pump26 based upon the measured time duration of the water flow through thetube.

In a further embodiment (FIG. 12), a sensor assembly 430 includes a flowelement in the form of a permanent magnet 431, a biasing device in theform of a spring 433, and a sensing device in the form of a proximityswitch 474. In the particular embodiment shown in FIG. 12, the proximityswitch 474 is in the form of a reed switch having contacts 475, 477sealed in a tube 479. The reed switch 474 is disposed outside of thetube 428 and is attached to the outside surface of the tube 428downstream of the magnet 431 and the spring 433. The sensor assembly 430can be used in place of the sensor assembly 330 in the dishwasher ofFIG. 10.

Both the magnet 431 and the spring 433 are disposed within the tube 428.As shown in FIG. 12, the magnet 431 is in the form of a hollow sleevehaving two opposite open ends for allowing the water to flowtherethrough in direction 86. A downstream end 441 of the magnet 431 hastwo oppositely polarized sections 443, 445. A magnetic line of force 447represents the direction of the magnetic flux between the sections 443,445.

The spring 433 has a downstream end 437 attached to the inside wall ofthe tube 428. An upstream end 439 of the spring 433 is attached to thedownstream end 441 of the magnet 431. The magnet 431 is not directlyattached to the tube 428.

During operation, the controller 342 applies a voltage to the valve 34to thereby allow water to enter the tube 428. As the water flows indirection 86, the magnet 431 is pushed in direction 86 against the biasof the spring 433, thereby compressing the spring 433. As the magnet 431moves in direction 86 to the position shown in FIG. 13, the contacts475, 477 become magnetized due to the proximity of the polarized section443, 445 of the magnet 431, as is well known to those skilled in theart. As a result of the magnetization of the contacts 475, 477, thecontacts 475, 477 attract each other and become electrically connectedto each other.

The controller 342 senses the electrical connection between the contacts475, 477. More particularly, the controller 342 can apply a smallvoltage to its output 359. If the voltage signal from output 359 istransmitted through the contacts 475, 477 of the switch 474 to the input361 of the controller, then the controller 342 determines that themagnet 431 is in the position of FIG. 13 and that water is flowingthrough the tube 428. Thus, the voltage transmitted through the contacts475, 477 and to the input 361 functions as a control signal.

When the water flow through the tube 428 stops, the spring 433 pushesthe magnet 431 in direction 387, opposite to direction 86. The movementof the magnet 431 back to the position of FIG. 12 results in thedemagnetization of the contacts 475, 477. The contacts 475, 477 are nolonger attracted to each other and physically separate such that thereis no longer an electrical connection therebetween. The electricalcontroller 342 senses the separation of the contacts 475, 477 by theloss or disappearance of the voltage on input 361.

The controller 342 can determine the time duration or time period of thewater flow based upon the status of the reed switch 474. Moreparticularly, the controller 342 can determine the time duration or timeperiod between the time at which the contacts 475, 477 are electricallyconnected and the time at which the contacts 475, 477 become separated.This time period corresponds to the time period between the point intime at which the magnet 431 is pushed in direction 86 by the water flowand the point in time at which the magnet 431 is pushed in direction 387at the cessation of the water flow. That is, the time period determinedby the controller 342 corresponds to the time period in which the waterflows through the tube 428.

The controller 342 can inhibit operation of the dishwasher elements 24,26 if the time duration of the water flow through the tube 428 isinsufficient to enable safe operation of the dishwasher elements 24, 26.Of course, the controller 342 can also inhibit operation of thedishwasher elements 24, 26 if there is no water flow through the tube428. More particularly, if the controller 342 does not sense anelectrical connection between the contacts 475, 477 after the valve 34has been opened, then the controller 342 inhibits operation of thedishwasher. Still more particularly, if the controller 342 does notsense a voltage at input 361 after the valve 34 has been opened, thenthe controller 342 does not supply a voltage to either the water heater24 or the water pump 26.

In a still further embodiment of the invention, a dishwasher 420 shownin FIG. 14 includes the flow sensor assembly 430, a relay 440 and thetimer module 42. The relay 440 includes a pair of normally closedcontacts 498, 500, and a pair of normally open contacts 492, 494.

During operation, manual actuation of the control knob 44 by the usercauses the switch 51 to close, thereby applying voltage from the voltagesource 56 to the timer motor 46. The timer motor 46 causes the cam shaft57 and the cam 48 to rotate, thereby closing the switch 49 and applyingvoltage to the valve 34. As the valve 34 opens, water flows from thewater source 85 and through the tube 328 in direction 86. The waterpushes the magnet 431 in direction 86 against the bias of the spring433, thereby causing the contacts 475, 477 of the reed switch 474 toclose, as discussed above. After the contacts 475, 477 close, electricalcurrent flows from the voltage source 56, through the coil 490, andthrough the reed switch 474 to ground. The excitation of the coil 490causes the contacts 498, 500 to open, thereby preventing the faultindicator lamp 438 from being powered on.

The excitation of the coil 490 also causes the contacts 492, 494 toclose, thereby connecting the voltage source 56 to the timer motor 46.This current path from the voltage source 56 to the timer motor 46through the contacts 492, 494 is in parallel with the current path fromthe voltage source 56 to the timer motor 46 through the switch 51. Asthe timer motor 46 continues to operate, the rotation of the cam 50causes the switch 51 to open, and then the only source of power to thetimer motor 46 is through the contacts 492, 494. Further operation ofthe timer motor 46 causes the switches 53, 55 to close, therebyconnecting the voltage source 56 to the heater 24 and the pump 26,respectively.

After operation of the heater 24 and pump 26, all four of the switches49, 51, 53 and 55 change their state substantially simultaneously. Moreparticularly, the switches 53, 55 open to remove power from the heater24 and the pump 26, respectively; the switch 51 closes to provide analternate power path to the timer motor 46; and the switch 49 opens toremove power from the valve 34. As the valve 34 closes and the waterflow through the tube 428 stops, the magnet 431 moves away from the reedswitch 474 in direction 387. With the magnet 431 farther away, thedemagnetized contacts 475, 477 of the reed switch 474 open, causing thecontacts 498, 500 to close and the contacts 492, 494 to open.

If water does not flow through the tube 428 when voltage is applied tothe valve 34, then the magnet 431 does not move in direction 86 and thecontacts 475, 477 of the reed switch 474 do not close. Further, nocurrent runs through the coil 490 and the contacts 498, 500 remainclosed, thereby causing the fault indicator light 438 to be powered on.The illuminated fault indicator light 438 visually indicates to the userthat there may be a leak or malfunction of the valve 34 that requiresrepair.

Another consequence of no current running through the coil 490 is thatthe contacts 492, 494 remain open. The rotation of the cam 50 causes theswitch 51 to open, thereby removing all power from the timer motor 46and preventing any further rotations of cams 48, 50, 52, 54. The openingof the switch 51 and the removal of power from the timer motor 46 stopsthe operation of the cams 52, 54 and prevents the cams 52, 54 fromcausing the switches 53, 55 to close. Thus, with the switches 53, 55remaining open, no power is applied to either the water heater 24 or thewater pump 26. As described above, the flow sensor assembly 430 is usedto prevent the application of voltage to the heater 24 and the pump 26if no water on which these dishwasher elements 24, 26 can operate isavailable in the tube 428.

In another embodiment (FIG. 15), a dishwasher 520 includes atemperature-sensing device in the form of a thermistor 530. Anelectrical controller 542 is electrically connected across thethermistor 530. The thermistor 530 has a resistance that changes withtemperature according to a known relationship. The thermistor 530 isdisposed in a water inlet conduit or tube 528. A water source 85, suchas a municipal water supply, a well, a water heater, or some combinationthereof, is fluidly connected to the water inlet tube 528.

In operation, the thermistor 530 detects a change in temperature and/ora flow of water within the water inlet tube 528. More particularly, theelectrical controller 542 places an electrical voltage across thethermistor 530 and measures and monitors the resulting current flowingthrough the thermistor 530. Because the voltage across the thermistor530 and the current through the thermistor 530 are known, the controller542 can also measure and monitor the resistance of the thermistor 530according to Ohm's Law. The current flowing through the thermistor 530has the effect of heating the thermistor 530 and thereby changing theresistance of the thermistor 530. For instance, the resistance of thethermistor 530 may rise with temperature.

The controller 542 uses the thermistor 530 to detect whether there is aflow of water through the tube 528 after the controller 542 opens thevalve 34. Before the valve 34 is opened, unless the dishwasher 520 hasbeen used recently, the temperature within the tube 528 is likely to bearound room temperature. After the valve 34 is opened and water flowsthrough the tube 528, the temperature within the tube 528 is likely todiffer from room temperature. Moreover, a flow of water across thethermistor 530 is effective in carrying heat away from the heatedthermistor 530, thereby reducing the temperature of the thermistor 530.

The controller 542 applies a voltage to the valve 34 in order to allowwater to enter the tube 528. Next, the controller 542 monitors thecurrent flowing through the thermistor 530, which is indicative of theresistance and temperature of the thermistor 530 according to a knownrelationship. If, as expected, the measured current of the thermistor530 changes by more than a threshold amount, which is indicative of thetemperature of the thermistor 530 changing by more than a thresholdamount, then the controller 542 determines that there is water flowingthrough the tube 528.

More particularly, the controller 542 can calculate a difference betweena thermistor temperature measured before the opening of the valve 34 anda thermistor temperature measured after the opening of the valve 34. Thecontroller 542 can determine whether the temperature difference equalsor exceeds a predetermined threshold that is indicative of water flow.If the temperature difference threshold is exceeded, the controller 542can then apply voltage to the heater 24 and the pump 26 since it isknown that these dishwasher elements 24, 26 have water available onwhich to operate.

Conversely, if the measured temperature of the thermistor 530 does notchange after voltage has been applied to the valve 34, then thecontroller 542 determines that there is no water, or an insufficientamount of water, flowing through the tube 528. The controller 542 canthen apply voltage to the fault indicator light 538 in order to indicateto the user that there may be a leak or a malfunctioning valve in needof repair. In this case, the controller 542 would inhibit operation ofat least a portion of the dishwasher 520. More particularly, thecontroller 542 would prevent the application of power to the heater 24and the pump 26 in order to prevent these dishwasher elements 24, 26from overheating in the absence of the cooling effect of water. However,even though the operation of the heater 24 and/or the pump 26 isinhibited, the controller 542 could continue operation of othercomponents of the dishwasher 520, such as the fault indicator light 538,for example.

The embodiment of FIG. 15 has been described herein as using the flow ofwater through the tube 528 to carry heat away from the thermistor 530.It is to be understood, however, that it is also possible to causeheated water from a water heater to flow through the tube 528 and addheat to the thermistor 530. In this case, the voltage applied across thethermistor 530 would have to be low enough that the temperature of thethermistor 530 before the opening of the valve 34 is below thetemperature of the water that is to flow through the tube 528. Thecontroller 542 would detect the flow of water by sensing a temperaturerise in the thermistor 530.

As described herein, the present invention advantageously increases thefunctionality of an appliance. While this invention has been describedas having a preferred design, the present invention can be furthermodified within the spirit and scope of this disclosure. Thisapplication is therefore intended to cover any variations, uses, oradaptations of the invention using its general principles. Thisapplication is intended to cover such departures from the presentdisclosure as come within known or customary practice in the art towhich this invention pertains and which fall within the limits of theappended claims.

1. A dishwasher, comprising: a water inlet within a dishwasher that isconnectable to a water source; a dishwasher element within thedishwasher that is operable on water received through said inlet; a flowsensor in fluid communication with said inlet and operable to generate acontrol signal indicative of water flow through said inlet, the flowsensor including a vacuum switch; and a control apparatus connectedbetween said dishwasher element and said flow sensor and operable toinhibit operation of said dishwasher element in response to said controlsignal.
 2. The dishwasher of claim 1, wherein said flow sensor includesa conduit and a venturi opening in communication between said conduitand said vacuum switch.
 3. The dishwasher of claim 1, wherein thecontrol apparatus includes a cycle controller configured to initiatetimed operation of said dishwasher element, said control apparatus beingconfigured to remove power from the cycle controller if the water is notflowing through the flow sensor.
 4. The dishwasher of claim 3, furthercomprising a valve in fluid communication with and disposed upstreamfrom the flow sensor, the cycle controller being configured to cause thevalve to open to thereby allow water into the flow sensor.
 5. The washerof claim 3, wherein said cycle controller is digital and configured tobypass the application of power to the dishwasher element in response tothe control signal.
 6. The dishwasher of claim 1, wherein the controlapparatus includes a cycle controller having a timer module configuredto initiate timed operation of said dishwasher element, said controlapparatus being configured to remove power from the timer module if thewater is not flowing through the flow sensor.
 7. The dishwasher of claim6, wherein the timer module includes a switch configured to selectivelyapply power to said dishwasher element, said control apparatus includinga relay configured to electrically connect said switch to a voltagesource dependent upon said control signal.
 8. The dishwasher of claim 1,wherein said control apparatus is configured to remove power from thedishwasher element in response to said control signal.
 9. The dishwasherof claim 1, further comprising a fault light connected to said flowsensor to illuminate in response to said control signal indicating thatwater is not flowing through the flow sensor.
 10. The dishwasher ofclaim 1, wherein said flow sensor is disposed downstream of said inlet.11. An apparatus for operating a dishwasher, comprising: a vacuum switchfor sensing a flow of water through a conduit in a dishwasher andgenerating a signal indicative of water flowing in the conduit; and acontrol apparatus for inhibiting an operation of the dishwasher inresponse to the signal from the vacuum switch.
 12. The apparatus ofclaim 11 further comprising: a venturi coupled between the conduit andthe vacuum switch, the venturi responding to water flow in the conduit.13. The apparatus of claim 12 further comprising; a timer module coupledto the control apparatus and the control apparatus being configured toremove power from the timer module in response to the signal generatedby the vacuum switch.
 14. The apparatus of claim 13 further comprising:a fault indicator coupled to the flow sensor so that the fault indicatorilluminates in response to the signal from the vacuum switch indicatingno water is flowing in the conduit.
 15. A method for controllingdishwasher operation comprising: detecting water flow in a conduit of adishwasher; generating with a vacuum switch a control signal indicativeof the detected water flow; inhibiting operation of a dishwasher elementin response to the control signal.
 16. The method of claim 15, the waterflow detection further comprising: detecting a differential pressure ina venturi coupled to the conduit.
 17. The method of claim 16 furthercomprising: illuminating a fault detector in response to the controlsignal.
 18. The method of claim 17 further comprising: removing powerfrom a timer module in response to the control signal.